changed the task to make it more appropriate

exercises/14_generics/generics3.rs

@@ -1,14 +1,13 @@
 // generics3.rs
 // Execute `rustlings hint generics3` or use the `hint` watch subcommand for a hint.
 
-// TODO Use your knowledge of generics to enchance the `stringify` function by only changing the signature.
-fn stringify(list: &[&str]) -> String {
-    let items_str = list
-        .iter()
-        .map(|e| e.to_string())
-        .collect::<Vec<String>>()
-        .join(", ");
-    format!("[{items_str}]")
+// This function should take an array of `Option` elements and returns array of not None elements
+// TODO fix this function signature
+fn into_dispose_nulls(list: Vec<Option<&str>>) -> Vec<&str> {
+    list
+        .into_iter()
+        .flatten()
+        .collect()
 }
 
 fn main() {
@@ -21,15 +20,35 @@ mod tests {
 
     #[test]
     fn store_str_on_list() {
-        let names_list = vec!["maria", "jacob", "kacper"];
-        let stringified = stringify(&names_list);
-        assert_eq!(stringified, "[maria, jacob, kacper]".to_string());
+        let names_list = vec![Some("maria"), Some("jacob"), None, Some("kacper"), None];
+        let only_values = into_dispose_nulls(names_list);
+        assert_eq!(only_values.len(), 3);
     }
 
     #[test]
     fn store_numbers_on_list() {
-        let numbers_list = vec![1, 2, 3];
-        let stringified = stringify(&numbers_list);
-        assert_eq!(stringified, "[1, 2, 3]".to_string());
+        let numbers_list = vec![Some(1), Some(2), None, Some(3)];
+        let only_values = into_dispose_nulls(numbers_list);
+        assert_eq!(only_values.len(), 3);
     }
+
+    #[test]
+    fn store_custom_type_on_list() {
+        #[allow(dead_code)]
+        struct Rectangle {
+            width: i32,
+            height: i32
+        }
+        impl Rectangle {
+            fn new(width: i32, height: i32) -> Self {
+                Self { width, height }
+            }
+        }
+
+        let custom_list = vec![Some(Rectangle::new(1, 2)), None, None, Some(Rectangle::new(3, 4))];
+        let only_values = into_dispose_nulls(custom_list);
+        assert_eq!(only_values.len(), 2);
+    }
+
+
 }

rustlings-macros/info.toml

@@ -746,13 +746,10 @@ name = "generics3"
 dir = "14_generics"
 hint = """
 Vectors in Rust use generics to create dynamically-sized arrays of any type.
-The stringify function takes a vector as an argument, but only accepts vectors that store the &str type.
+The `into_dispose_nulls` function takes a vector as an argument, but only accepts vectors that store the &str type.
 To allow the function to accept vectors that store any type, you can leverage your knowledge about generics.
 If you're unsure how to proceed, please refer to the Rust Book at:
 https://doc.rust-lang.org/book/ch10-01-syntax.html#in-function-definitions.
-
-*Please note that in `stringify` we want to use `.to_string()` on vector elements
-Refer to this: https://doc.rust-lang.org/book/ch10-02-traits.html
 """
 
 # TRAITS

solutions/14_generics/generics3.rs

@@ -1,17 +1,13 @@
 // generics3.rs
 // Execute `rustlings hint generics3` or use the `hint` watch subcommand for a hint.
 
-// Here we add generic in function declaration so function can work with different types
-fn stringify<T>(list: &[T]) -> String 
-where
-    T: ToString // here we also specify that T needs to implement ToString trait so we can use .to_string() on the vetor elements
-{
-    let items_str = list
-        .iter()
-        .map(|e| e.to_string())
-        .collect::<Vec<String>>()
-        .join(", ");
-    format!("[{items_str}]")
+// Here we added generic type `T` to function signature
+// Now this function can be used with vector of any
+fn into_dispose_nulls<T>(list: Vec<Option<T>>) -> Vec<T> {
+    list
+        .into_iter()
+        .flatten()
+        .collect()
 }
 
 fn main() {
@@ -24,15 +20,32 @@ mod tests {
 
     #[test]
     fn store_str_on_list() {
-        let names_list = vec!["maria", "jacob", "kacper"];
-        let stringified = stringify(&names_list);
-        assert_eq!(stringified, "[maria, jacob, kacper]".to_string());
+        let names_list = vec![Some("maria"), Some("jacob"), None, Some("kacper"), None];
+        let only_values = into_dispose_nulls(names_list);
+        assert_eq!(only_values.len(), 3);
     }
 
     #[test]
     fn store_numbers_on_list() {
-        let numbers_list = vec![1, 2, 3];
-        let stringified = stringify(&numbers_list);
-        assert_eq!(stringified, "[1, 2, 3]".to_string());
+        let numbers_list = vec![Some(1), Some(2), None, Some(3)];
+        let only_values = into_dispose_nulls(numbers_list);
+        assert_eq!(only_values.len(), 3);
+    }
+
+    #[test]
+    fn store_custom_type_on_list() {
+        struct Rectangle {
+            width: i32,
+            height: i32
+        }
+        impl Rectangle {
+            fn new(width: i32, height: i32) -> Self {
+                Self { width, height }
+            }
+        }
+
+        let custom_list = vec![Some(Rectangle::new(1, 2)), None, None, Some(Rectangle::new(3, 4))];
+        let only_values = into_dispose_nulls(custom_list);
+        assert_eq!(only_values.len(), 2);
     }
 }